Textile materials, especially synthetic fibers, are employed in various fields, such as apparels and industrial textiles. Among various synthetic fibers, polyester fiber and acrylic fiber are hydrophobic and have poor moisture absorbability and antistaticity. Garments and bedclothes produced with such hydrophobic fibers give very uncomfortable sticky feel to wearers in a sweat, in other words, deteriorate the comfortableness of wearers. This has been the disadvantage of those fibers comparing to natural fibers. For solving such problem, JP-A 2002-38375 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposed a process wherein hydrophobic synthetic fiber is modified to be hydrophilic by graft-copolymerizing such synthetic fiber with water-absorptive organic fine particles comprising of carboxylate radicals and cross-linked acrylic polymer; and JP-A 6-16952 proposed a process wherein hydrophobic synthetic fiber is modified by imparting the moisture absorbability of natural substances to synthetic fiber through adding natural substances in fiber-forming polymer or fixing natural substances or amide-modified proteins onto synthetic fiber with the aid of resin binders. However, those processes required complex and numerous processing steps and high cost, and the synthetic fiber treated with resin binders exhibited uncomfortable hand. Japanese Patent 2995442 proposed a process wherein film of fibroin and graft-copolymer is formed on fiber surface. The film formed in this process is not durable due to the insufficient number of sites of reaction between fibroin and graft-copolymer.